Comcast, the biggest cable provider in the U.S., won a lawsuit against the Federal Communications Commission that could have serious repercussions on how the internet is regulated. At stake is the principle of "net neutrality." But what does that mean, how does this decision affect it, and what will it mean to you? (Watch an overview of net neutrality.) A brief guide:

What is net neutrality?In basic terms, it's the idea that all internet users should have unrestricted access to all legal content, services, and sites on the web. In practice, this means that Comcast and other internet providers shouldn't be able to block or curb their customers' access to certain categories of sites — bandwidth-heavy video services YouTube and Hulu, for example — or specific sites, such as those owned by competitors.

How is net neutrality maintained?In some countries, including Italy, Russia, and Japan, net neutrality is enforced by laws. In the U.S., however, it has been more or less voluntary. In 2005, the FCC set out four "Open Internet Principles" it expects internet providers to follow, and the current FCC board is currently considering making those four net-neutrality guidelines, plus two others, official FCC regulations.

Where does Comcast come into it?In August 2008, the FCC, citing the 2005 guidelines, ordered Comcast to cease blocking and/or slowing customers' access to BitTorrent, a peer-to-peer site that facilitates the sharing of large (and sometimes pirated) music, movie, and software files. The federal appeals court in Washington, D.C. unanimously ruled Tuesday that the FCC did not have the legal authority to tell cable-based internet providers how to manage their network.

What does this mean for you?In theory, Comcast could "go back to throttling BitTorrent" and other services -- other providers like AT&T, Time Warner, and Verizon could follow Comcast's lead. Internet providers may now "block access to certain kinds of traffic, or give preferential treatment to other traffic," says Eric Savitz at Barron's, radically changing how we use the web. Or else Comcast's win "means very little," says Marguerite Reardon in CNET News: Contrary to the fears of net-neutrality advocates, broadband users "are not likely to see any change in their service as a result of this court ruling."

Should the FCC be able to regulate the internet?It depends who you ask. Net neutrality proponents argue that we need federal regulation, since the internet is now a necessity rather than a luxury. But free-market advocates say increased regulation would hamper innovation. Some conservative commentators, including Glenn Beck and Rush Limbaugh, also argue that FCC regulation would allow the government to "censor content" and "squash dissent."

What happens now?The FCC says it will continue working on its own net neutrality rules. But if it wants more regulatory powers, it either needs new legislation from Congress or it can reclassify broadband as a "common carrier" service, like landline telephones, that falls under its existing regulatory authority. The latter option, sometimes called the "nuclear option," is favored by net neutrality activists, but would almost certainly face a court challenge.